The present invention relates to indicator lamps especially for motor vehicles.
It applies in particular to the indicator lamps of the xe2x80x9cthird stop lightxe2x80x9d type, that is to say braking-indicator lamps, which can be mounted within the passenger compartment of the vehicle, against the rear window of the vehicle, or be integrated into slim appendages situated at the rear of the vehicle, such as aerodynamic spoilers or ailerons.
The first lamps of this type exhibited the drawback of providing non-uniform illumination, despite the devices used for spreading the light, which generally consisted of balls or rings integrated into the enclosing glazing or into an optical plate of the lamp situated downstream of the light source. This drawback, although it is generally tolerable from the point of view of the regulations and of the photometry, is prejudicial from the aesthetic point of view, which is becoming increasingly important nowadays.
A single-source lamp is known, for example from the document FR-A-2 614 969, the illumination from which is uniform. This lamp comprises, in a housing, a transparent or translucent optical screen, more usually called xe2x80x9clensxe2x80x9d or xe2x80x9cballoonxe2x80x9d, interposed between a single light source and an essentially flat optical plate and extending in a direction perpendicular to the optical axis of the lamp. The particular geometric configuration of the lens ensures that the surface density of luminous flux arriving on the plate is essentially constant over the entire surface of this plate. Moreover, the surface of the plate is provided with striations straightening out the light rays originating from the lens so as to transmit to the outside a beam situated in the solid angle intended by the regulations.
However, motor-vehicle constructors currently want to be able to use third stop lights at least one of the dimensions of which, for example the width, is relatively large, and which employ a plurality of light sources such as light-emitting diodes. One solution to this problem consists, according to the document FR-A-2 776 595, in producing a device consisting of the combination of optical subassemblies as described in the document FR-A-2 614 969, and exhibiting uniform illumination within each subassembly.
The document FR-A-2 776 595 provides for several light sources to be used, and, for each light source, a hemispherical lens distributing the light uniformly in a plane essentially perpendicular to the general direction of emission, onto a second, generally plate-shaped, element able to straighten out the incident light towards the general direction of emission, and, at the transition between two adjacent plate-shaped elements, at least one striation is provided which is capable of straightening out, towards the general direction of emission, the light originating from two adjacent light sources each associated with one lens and with one plate-shaped element.
Such a design gives satisfaction on the photometric front, but remains capable of improvement, especially as regards its mechanical construction. This is because the various components, such as the light sources, the hemispherical lenses and the plates, are mounted on a support structure. It results therefrom that the construction or the assembling of such an indicator lamp constitutes a relatively intricate operation, which it is very difficult to automate. Moreover, slight variations in the respective positions of the various optical components, resulting from their respective manufacturing tolerances, have the consequences of substantial variations in the photometric qualities of the resulting beam.
The present invention is placed in this context, and its object is to propose an indicator lamp using several light sources, which is simple to assemble, the photometric qualities of which are constant from one lamp to another, and which is inexpensive.
Hence the subject of the present invention is an indicator lamp for a motor vehicle comprising a plurality of light sources and optical processing means able to straighten out the light emitted by the light sources so that it is propagated in a direction essentially parallel to a general direction of emission, the optical processing means comprising, in association with each source, a first element able to distribute the light in a plane essentially perpendicular to the general direction of emission, in an essentially uniform way onto a second, generally plate-shaped, element able to straighten out the incident light towards the said general direction of emission.
According to the present invention, linking elements are arranged between first adjacent elements and between the first elements and the second element, and the first element, the second element and the linking elements are made together of the same material and form a one-piece optical structure.
According to other advantageous and non-limiting characteristics of the invention:
the optical structure further includes, between the linking elements and the second elements, junction elements which are of a single piece with them,
the second, plate-shaped, element includes a stiffening rib all along one of its longitudinal edges,
the optical structure, between the second element and the first elements or the linking elements, includes a continuous plate which is of a single piece with these elements,
the optical structure includes elements for fixing a printed circuit,
the printed circuit carries the light sources,
the light sources are light-emitting diodes,
the light sources are essentially aligned,
the optical structure includes means for retaining a connector associated with the printed circuit, these retaining means being of a single piece with the optical structure,
the optical structure includes means for fixing into a housing, which are of a single piece with the optical structure, and
the first element distributes the light onto the second element, taking account of the variations in the transmission coefficients of the first and second elements, and of the emission-pattern curve of the light source, in order to obtain an illumination at the exit from the second element which corresponds to a predetermined law.
A further subject of the present invention is a method of manufacturing an indicator lamp for a motor vehicle, the lamp comprising at least one light source and optical processing means able to straighten out the light emitted by the light sources so that it propagates in a direction essentially parallel to a general direction of emission, the optical processing means comprising, in association with each source, a first element able to distribute the light in a plane essentially perpendicular to the general direction of emission, in an essentially uniform way onto a second, generally plate-shaped element able to straighten out the incident light towards the said general direction of emission, the method comprising the stages consisting in:
establishing a law of change of the transmission coefficients of the optical processing means as a function of at least one co-ordinate on the plate in a direction perpendicular to the general direction of emission,
establishing a desired law of change of the illumination of the lamp as a function of the co-ordinate on the plate.
According to the present invention, the method further comprises the stages consisting in:
determining the emission-pattern curve of the light source and the corresponding emission law,
establishing, by combining these laws, a relationship between the orientation of a ray originating from the light source and incident on the second element and the co-ordinate on the plate,
defining the geometry of the optical processing means as a function of the said relationship,
manufacturing a mould, by using the said geometry, for at least the first element,
moulding the first element by the use of the said mould.